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Duration of treatment for patients with mCSPC

Bobby Liaw, MD: Once patients have started treatment for metastatic castration-sensitive prostate cancer – with the exception of docetaxel which ends after 6 cycles of treatment – how other agents targeting the androgen receptor pathway have been studied is to start them and continue them for as long as possible. we find that they still demonstrate disease control. As long as we don’t run into any tolerance hurdles due to side effects.

Most patients will stay on one of the AR-led therapies for some time, depending on the medication you are taking. Depending on the study you are looking at, the duration of the study will vary. For example, in the TITAN study of apalutamide, the median duration of treatment for patients who received apalutamide was 39 months. But if you look at other studies, such as LATITUDE for abiraterone, the time to next line of treatment was 54.9 months. This doesn’t necessarily mean they took the drug all the time, but it is how long it took them to move on to the next line of treatment. Now that’s a significant amount of time that people are on treatment. And certainly there will be patients who experience side effects. For many patients who may have difficulty tolerating, we have several ways around this, either by interrupting the dose by suspending treatment or by reducing the dose. As for the people in the study who interrupted their treatment with the various antiretroviral drugs, it’s about 10%, 12% of the people. It’s harder to quantify exactly how many people have these reductions and whether or not they were able to recover the full dose. But a common question patients will ask regarding any dose maintenance or dose reductions is: what impact does this have on my treatment? What impact does this have on the control of my disease? To be honest, it’s a little harder to tell, as we don’t have a lot of solid clinical trial data here to cite. However, we know from earlier phase studies that lower doses of drugs, whether abiraterone, enzalutamide or apalutamide, were always associated with a significant antineoplastic effect. But I think at the end of the day, we all feel that a clinical response is most likely optimized at full dose and full density.

I will refer to TITAN again, just to use apalutamide as an example, but in this study 7.1% of patients required dose reduction, and these patients were still included in the overall analysis. And the overall analysis still shows that we still see a consistent clinical effect of the drug for people on the reduced dose.

Transcript edited for clarity.